KEY POINTS:
Anyone who has had their holiday road trip brought to a standstill by an overheated car engine will know how easily it can happen.
Engines burn a mixture of petrol and air, which then combust in the cylinders. Rapid expansion from the explosions pushes the cylinders down, producing the power to drive the car.
Much of the energy from each explosion does not do any work at all and is lost as heat. Over a short period of time, an engine can produce considerable amounts of heat. In fact, your engine can get hot enough to melt or weaken some of its parts.
The whole engine doesn't have to overheat for a failure to occur. If a single engine part is compromised, the car will stop.
Here are a few helpful hints to avoid spending time on the side of the road, waiting for an AA rescue.
There are still a number of air-cooled engines on the road. These are designed with cooling fins surrounding the cylinder heads. Air-cooled engines must have open access to incoming air in order to cool properly.
The advantages of air-cooled engines are that they have simple cooling systems that are lightweight, and do not have a cooling system, or water pump to go wrong.
Disadvantages are that they require ample fresh air in order to remain cool, and it is more difficult to precisely control the overall engine temperature.
Modern car engines are all liquid-cooled. The primary advantage of using liquid cooling is that the engine can be placed in a location with tight confines that doesn't require very much air passing over it to cool.
Disadvantages include increased weight, and the potential to develop localised hot spots. The engine is cooled by the flow of liquid through channels built into the engine. It then travels through a temperature-activated valve, called a thermostat. After passing through the thermostat, the coolant goes into the radiator, where it is cooled by air.
The fluid then travels back into the engine.
The engine is cooled by water and ethylene glycol (anti-freeze). Adding anti-freeze to the system reduces the freezing temperature of the fluid in the cooling system. Anti-freeze also raises the boiling temperature of water so that it can absorb more heat than water alone.
Most cars use half anti-freeze and half water for the cooling system. Never use water alone in your car's cooling system. Always make sure your car has sufficient coolant.
The thermostat measures the coolant temperature and opens a valve when the coolant reaches a sufficient operating temperature. If the thermostat is broken, then the fluid in the engine will recirculate in the engine and bypass the radiator. The engine will quickly overheat. You can test for a broken thermostat by feeling the temperature of the coolant return hose to the radiator. The hose should become hot within minutes of starting the car.
There are two types of fans: electric and belt-driven. Electric fans turn on and off according to temperature sensors. Belt driven fans should be checked, with the engine and ignition off, by trying to spin the fan by hand. It should not turn easily. If it does, the fan clutch may need replacing.
Coolant fluids may become low if there are any leaks in the system.
If the car appears to be running hot, visually check for leaks while the engine is running. Check all of the hoses that feed the radiator. Also check that the radiator is not leaking. Finally, check the water pump for leaks. A worn-out water pump will leak water out of an overflow hole. If your water pump is leaking, replace it right away.
Finally, with the engine running and the hood up, watch for leaks around the radiator cap. If you notice any liquid escaping, replace the cap. Never open a radiator cap when the fluid may be hot.
Next, remove the oil cap and check for a white goop underneath the cap. If water is getting into places it shouldn't in the engine, it will mix with oil and produce a white gel. The only fix for internal water leaks is to take the car to a professional.
If engine temperature begins to rise when driving, slow down and turn the heater on and find a safe place to stop.
Always carry a bottle of water in the boot and if the leak is not too bad, wait until the engine cools down, top up the radiator and make your way slowly to the nearest garage.
